From Bugzilla Helper:
User-Agent: Mozilla/4.0 (compatible; MSIE 5.5; Windows NT 4.0)
BuildID: 2002072104
If you have a list (OL or UL) in which the last element of each LI is a image
with the style foat : right, the right-hand ?margin? will grow with each
addition LI element in the list.
Visit the URL supplied for an example. The page is very simple and only
contains one list.
Reproducible: Always
Steps to Reproduce:
Visit the supplied URL.
Actual Results: Page isn't displayed properly.
Expected Results: Each of the img element should be aligned vertically and the
paragraphs of the LI elements should not be shrinking in width.

It isn't the right margin that's increasing, it's the width of the li that's
decreasing because the images are in its way. You can see verify this by adding
a border to the list items[1]. Forcing the width of the li to 100%[2] seems to
generate the desired result.
[1] li {border: 1px dotted blue;}
[2] li {width: 100%;}

I believe this bug is valid. I have a testcase (soon to be attached) that shows
the 'li' elements getting more narrow at each float, which is not correct under
CSS2. The floats can certainly end up next to each other in a stair-step effect
like we see in the testcase, but only if they're next to each other, which isn't
happening here. Either way, the 'li' elements should all be the same width (the
width of the parent), and they aren't.

Platform/OS -> All.
Ok, so according to CSS 2 it seems only the actual inline content should be
affected directly by the floats.
Does "-moz-float-edge: margin-box;", as I guess, make the list item flow around
the floats' margin-boxs? If so, can we remove it? (since removing that property
does indeed render the attachment corectly)

Please look at the bottom of this page:
http://www.lecb.ncifcrf.gov/~toms/LeftHanded.DNA.html
and you will see that this bug is completely destroying my web page. It is making
me want to abandon mozilla, but there is no better browser!
CAN THIS BE LOOKED AT AND FIXED PLEASE? It's been hanging around for three
years!!!! It just had its third birthday!

Here's another testcase, at least it seems to be the same bug:
http://www.julianstahnke.de/problem/
Giving the <code><li></code> a <code>width:100%</code> fixes it, but then you
can't apply any padding or margins to it, which is not very fortunate.

(In reply to comment #25)
> Oh, and that bug exists in Firefox 1.5, too. If that helps.
I confirm. It failed in Firefox:
Mozilla/5.0 (Macintosh; U; PPC Mac OS X Mach-O; en-US; rv:1.7.10) Gecko/20050716
Firefox/1.0.6
It worked fine in Safari Version 2.0.1 (412.5)
Exploiter 5.2 for mac failed in a different way, it didn't wrap
the text around the image at all, putting it on the far right
and then ignoring that for the rest of the page.
I'm glad this is a problem in firefox - the supposedly hot new perfect
browser. Maybe that could goose someone to fix the problem?
Isn't this just trivial? Somewhere there is just a parameter that is
being changed that should not be!

I just ran into this bug today. Looking through Bugzilla, I discovered that it's been reported many times (bug #143162, bug #321583, etc.). It has been over a year since the last comment on this big and 4.5 years since it was first reported.
I don't appear to have the ability to add votes to this bug, but I would like to add my voice those urging that its priority be raised. It causes significant layout problems for some pages.
I am a programmer and am willing to help, but don't have the necessary familiarity with the layout code or the moz-float-edge property. If you believe it is more efficient for me to pick up this knowledge and contribute to fixing the problem than to have it fixed by someone who already has this background knowledge, let me know.

It would be great for this bug to stay alive. Firefox seems to be the only modern browser to do this wrong, which is a total shame. Lists and floats are pretty common things that are nice to be able to mix together.

...just as an FYI to some would-be fixer of this bug in some unspecified future date...
...or to anyone looking for a reasonable work around... Firefox does not choke on definition lists in the same way. It seems weird to me that the <dl> list would be handled differently from the <ol> or <ul> lists, but it looks like it is.
I guess I will start using <dl>'s a lot more now and if I need a bullet, I will style one in there.